1. Field of the Invention
This invention relates to a thin-film transistor and an active matrix liquid crystal device provided with thin-film transistors of this type.
2. Description of the Related Art
Thin-film transistors (hereinafter, referred to as TFTs) are broadly divided into the stagger type, the reverse stagger type, the coplanar type, and the reverse coplanar type. Of these, the arrangement of the reverse stagger type is shown in FIGS. 1 and 2 and will be explained below.
Referring to FIG. 1, a gate electrode 2 consisting of a metal such as tantalum or chromium is formed on an insulating substrate 1 made of glass or the like, and a gate insulating film 3 is formed on the gate electrode 2. An i-type semiconductor film 4 consisting of i-type amorphous silicon (i-a-Si) is formed on the gate insulating film 3 so as to oppose the gate electrode 2. Source and drain electrodes 5 and 6 made of a metal such as chromium are formed on the i-type semiconductor film 4, respectively, through n-type semiconductor layers 7 and are spaced apart from each other by a predetermined distance to form a channel region. Each n-type semiconductor layer 7 consists of n-type amorphous silicon (n.sup.+ -a-Si) doped with an impurity. A protective layer (not shown) is formed to cover the entire structure.
This type of thin-film transistor and a TFT matrix array composed of these TFTs arranged in matrix have been manufactured by the method described below. Table 1 lists the requirements concerning the manufacturing steps for a conventional thin-film transistor and a TFT matrix array. In this case, the reverse stagger type of FIG. 1 is taken up as an example.